rdtompki

The Al spider does seem very stiff and Al won't have the same fatigue characteristics as the all-steel BB7 rotor, but we're only asking the rotor to move maybe .5mm? Time will tell.

Ritterview

Thanks for obtaining that weight, it isn't otherwise available. But does the Avid 203 mm G2 rotor weigh 230 grams? I just weighed my Avid 203 mm, and it was 184 grams. This is similar to other weights seen on image searches.



I think it is the Avid 203 mm G3 that weighs 222 grams.

twocicle

The older Avid 203mm rotor I weighed is from circa 2003-2004. It's not the wavy cleansweep style, just has a few notches in the outer edge.

Just verified it does weigh 230gm on my digital scale and the same weight as the G3 I had (since returned as not needed).

FWIW. My scale is a cheap POS and no scientific marvel, but the G3 I had measured is within 8gm of the Kern photo.

Ritterview

Might you update us on the performance of the RT86? Does that aluminum sandwich handle heat better than a steel rotor such as the Avid G2/G3?

twocicle

I have no technical data (temp sensor) but so far have only managed to "warm" the rotor. No massive hill descents yet. Otherwise, performance to date has been great.

sine

If I may.....

Based on our experience in France this past April, the Shimano ICE rotor (at this time front only) does handle heat much better.

After one 10 mile descent, the top including many switchbacks, I checked and could feel the heat coming off the disc, but the al spider was warm to the touch. Braking (with EBC Gold pads) was great, one finger, and when needed, full three finger full stop when I messed up one corner (entering a bit too fast). This was our biggest braking test. We did other descents with switchbacks during the trip but not as long nor with the long straights. We were close to Ventoux but the top was not open so we did not go up.

I was not impressed with the BB7 when used with stock pads and either roundagon or G3 discs. But with the ICE disc and EBC gold pads it works great.

ksisler

I basically like the idea, but dread the thought of a flock of runaway, swerving, attention-disconnected bikers running over my @&& because they are fixated on watching their e-toys... oh well, we already have that problem don't we? But at least in this case it would be for brake measurements and alarm data such that their demise might contribute to humanity in some small way! Maybe such as tool could be built that grabs the sensor temp, data/time, and GPS location and sends it to a twitter account but that the device be hard blocked from receiving the data itself unless the speed is zero... oh and a little airbag and a skid plate also! [

PMK

Not much different, the part about having your butt run over, than if they can't stop because the discs are overheated and pads smoked.

PK

twocicle

What in-flight e-toys were you referring to exactly? Are you confused about Sine's comment of checking the disc warmth by hand (getting off the bike for a manual check)?

PDub62

This is the first I've seen this thread and wanted to provide some info on a brake failure we had w/ a Santana w/ the WinZip disk brake on the rear. We were touring in the Adirondacks pulling a BOB trailer; we had only had the bike for a couple of months so I hadn't had to do any maintenance w/ the brake up to that point. Coming down a long, steep, straight stretch I was feathering the rear brakes to keep our speed under 35 mph when we flew by a museum that my wife wanted to stop at so I started to get on the brakes harder so we could stop and turn around. As I did that the rear brake started sqealing super loud and faded away to nothing; luckily I was able to stop using just the front brake but it took a while and scared the heck out of us. Since my confidence in that much touted brake was pretty well shot, when we returned home from the trip I added a rim brake on the rear wheel w/ a cyclocross brake lever. Now if the disk brake fails again I have another option to help me stop. In general I like having the disk brake because of its stopping power but it's nice to have a backup. We have a newer Cannondale road tandem w/ disks but we've never taken that into any mountainous areas and probably won't after reading about the risks in this thread!

CaptainHaddock

Not knowing how big the decent was, so I can't say that my experiences have been the same, other than to comment that I descend with my wife and dog in his Burly Nomad (making a team weight of about 340) and have not had any problems at this point. Further I feel like it should be pointed out that you yourself state that you had not performed any preventative maintenance at that point, and you may very well have caused your own problem.

jacks1071

We're running 203mm avid disc's with Bengal MB700T calipers. Its a very powerful combo, we had Avid BB5's previously with 160mm rotors and that combo was barely acceptable in the flats - terrible in the hills, subject to serious brake fade.

Once my rotors are toast I plan to run a down-hill type floating rotor. The 203mm Avid's do a good job at stopping the bike but they warp/bend very easily, we do a climb every week that we have to come back down, 11% average gradient but its 28% in a few spots and my rotors warp a little pretty regularly - I just straighten them out which only takes a few minutes but its annoy to be doing it every week or two. That being said I'm determined to wear them out before replacing.

akexpress 

We just completed Cycle Oregon and had one descent that was about 15 miles long with some sustained grades of -9 to -10%. As there were mannnny singles it was hard to let the tandem run. We have been trying many brake combinations on our Calfee after an Avid failure on Mt Ventoux last summer. We switched to the Bengal MB700T calipers with avid rotors at that time. I was less then pleased with the avid rotors over the past year. We also have a Ventana full suspension mt tandem that we run Hope V2 brakes on and have been very pleased with the Hope rotors and how quiet they are. Long story short is we switched to a Hope V2 rotor and ebc sintered pads in the Bengal and are very pleased with the performance and quietness they exhibited. We did have a little pad wear after the week of riding with a lot of climbing and descents but less then our friends whom used an all Avid combination.

PMK

Not regarding the road tandem, but it could, which EBC pad material did you go with. We have good luck overall with oem AVID pads in the dry, in the wet it's as if the pad material is made from sugar and melts away quickly. I am considering some brake changes to the Ventana, mainly for better wet ride longevity.

PK

PMK

FWIW, here is the Bengal catalog.

https://www.bengalperformance.com.tw/...cxMV9PRU0ucGRm

PK

cafzali

Is it just me or do others think that disc brakes are a solution to a non-existent problem? If you really get down to brass tacks, the current braking systems are only really ever an issue with carbon rims, given their lower rate of heat dissipation. Granted, there is a big segment of folks, including myself, who ride on CF frames, but the number of people who are riding around with full carbon bikes including wheels is relatively small. While many may consider them a "nice to have," those folks would be the only ones who are really keenly interested in disc brakes.

StanleyJ

... and for 2013 (available Oct. 2012), Hope will replace the current V2 brake with the V4, a 4-pot brake with a pair of 16mm pistons (same as current M4) and a pair of 18mm pistons (versus a just a pair of 25mm pistons in the V2). Better heat management coupled with a new brake pad, it gives a bigger braking surface than the current V2, whilst using the same saw-tooth rotors as the X2/M4 brakes... or an all-new vented rotor:

V4 calliper: https://www.bikeradar.com/mtb/gallery...e-2012-35126/2
V4 vented rotors: https://www.bikeradar.com/mtb/gallery...e-2012-35126/4

As the V4 sits in-between the current M4 and soon-to-be-replaced V2 in terms of hydraulic fluid that needs to be pushed... I asked Hope about how well would the V4 callipers work is paired with the cyclocross/road ride disc-brake remote-mastercylinder, the V-Twin. To that they answered the lever travel will be a bit more, though it would work. Plus as the pads wear, the mastercylinder would need to be topped up with fluid. Alternatively, like the guys on MTBs whom pair the "Race" brake levers with V2 calipers, is to overfill the mastercylinder ever so slightly from the get go... so that the pads sit closer to the rotor anyway. Hope rotors are true enough that the closer pads shouldn't drag. Whilst V-Twins paired with M4s (with Hope floating 203mm rotors) should already be plenty for a road tandem... British "Landescape" brand tandems already spec them on their fancy carbon tandem: https://www.thetandemshop.com/landescape.html

That said, I wager Hope M4 calipers would play nice with V4 vented rotors... however wouldn't know unless one tried it (rotor is thicker by about 1mm). That or prod Hope once more with questions...

joe@vwvortex

Let me ask this question - do you really need disc brakes on your car when for all those years we had drum brakes which were more than adequate to stop the vehicle?

rdtompki

+1. team weight, weather, terrain all enter into one's decision of course, but there is plenty of evidence that a number of teams (to say nothing of MTB riders) prefer disc brakes, ether rear-only or front/rear. Rim brakes may be at the tail end of technology development, but Shimano's introduction the the ICE XT brakes has shown that there are still advances being made in the disc arena; I find the ICE XT rotor to be superior to the Avid rotor on the back of the tandem.

I think we would all agree that a certain amount of "slop" in the rear brake, whatever the technology, is an on and off problem with tandems. I look forward to the day when a company develops hydraulic calipers that are tandem-friendly. Many of us would go to these in a New York second (whatever that is).

Shimagnolo

You have never:
- Driven a 1967 Camaro (w/o disc option).
- Driven a Jeep CJ-5 a day after driving thru mud when the mud inside the brake drums has dried into a powder.

joe@vwvortex

Umm - I've driven plenty of cars with drum brakes. Have you descended 10% plus grades in a Type II VW bus full of your friends?

However - I have descended on a MTB in the mud with an under the bottom bracket U-brake........

merlinextraligh

When it comes to tandems, I think it is largely you. There are clearly circumstances where rim brakes are at least a definite limitation, and at worse an actual problem.

We've done descents in the Appalachias, (such as Brasstown) that are very steep and twisty, where the absence of disc brakes limited how fast we could descend. Coming down Brasstown, we were melting the pads, lstening to , and smelling the offgassing as the pads essentially liquified. By the bottom we had virtually no brakes, and would have had to stop and wait had the descent been any longer.

On the backside of Hogpen (where you could easily hit 75mph if you let it run) we stopped to let the brakes cool.

In both instances, disc brakse would have been a major advantage.

That said, we choose to use calipers, because in most instances for us they are more than adequate. Descending off Mt Bachelor at Masters Nationals, and the descents in Everest Challenge, with speeds in the mid 60's, calipers were fine because the descents were long fast, but also relatively straight.

But if we were racing in hilly terrain on the east coast, absolutely would use a rear disc, and without it, you'd be at a significant disadvantage.

cafzali

But this is a very specialized situation and not one that the vast majority of cyclists will ever find themselves in. What prompted this thread was a discussion on disc brakes on road bikes. In this scenario, traditional caliper-based brakes remain more than adequate for the vast majority of people who aren't professional racers or don't have carbon rims. To me, that says it's likely to be a niche market, no matter what, just like CF frames are a niche market, etc.

joe@vwvortex

Living in the Bay Area and next to the foothills and Sierras - not to forget the Coastal Range - we find ourselves in situations like that all the time. I have way more confidence in descending with disc brakes on the tandem then I ever did with canti's or V-brakes.

PMK

So, if we do away with our Avid disc brakes, it sounds like rim brakes are not a great choice either. I did some research on replacements and wondered, is rope or chain better when just using an anchor for slowing and stopping. Chain could be more compact for a given volume vs strength, but may weigh more, whereas a rope may have some inherent stretch, and therefore some lag before fully applying the brake.

Decisions like this become almost mind numbing.

PK